Milepost 31 is an award-winning information center that highlights the people and projects that shaped Pioneer Square, and provides an inside look at the SR 99 Tunnel Project. There, you'll find more than just construction photos and brochures. You’ll find history, artifacts and interactive exhibits designed to broaden your understanding of the land beneath you. You’ll explore the neighborhood’s changing landscape, from earth-moving efforts of the past to the massive tunnel project that will soon move State Route 99 underground and reconnect Pioneer Square to the waterfront.
Location and hours
211 First Ave. S., Seattle
Admission is free.
11 a.m. to 5 p.m. Tuesday - Saturday (closed on state holidays).
Open until 8 p.m. on the first Thursday of each month during the Pioneer Square Art Walk.
Events and activities
First Thursday Speaker Series - Bertha and Progress on the SR 99 Tunnel Project
April 3, 2014
6 – 6:30 p.m.
You’ve been hearing a lot lately about our efforts to replace the State Route 99 Alaskan Way Viaduct. This is a big, complex undertaking. And as we all know, we’ve encountered some challenges. Join Matt Preedy, Alaskan Way Viaduct Replacement Deputy Program Administrator, as he explains how WSDOT and STP are addressing these challenges and what the plan is to get Bertha, the SR 99 tunneling machine, moving again.
Make Your Own Mobile
March 15, 2014
1 – 4 p.m.
Join us at Milepost 31 for a monthly kids’ craft event and make your friends green with envy (pdf 699 kb). Take the opportunity to learn more about Bertha, the world’s largest tunneling machine, while also expressing your creative side. Kids can create a Bertha inspired four-leaf clover mobile in celebration of St. Patrick’s Day.
History Scavenger Hunt
April 19, 2014
1 – 4 p.m.
Join us at Milepost 31 for our monthly activity for kids. This month we’re hosting a scavenger hunt eggstravaganza (pdf 1041 kb) to discover Pioneer Square’s rich transportation history. Hop on down with your family and friends to explore historic icons and hidden gems in Seattle’s oldest neighborhood. Test your knowledge, check out cool new Pioneer Square locales, and enter to win a grand prize furnished by the Alliance for Pioneer Square. Pick up your scavenger hunt kit at Milepost 31 between the hours of 1 and 4 p.m.
Take a self-guided tour (pdf 466 kb) of the SR 99 Tunnel Project's massive work zone. Walk or bike along the paved path west of the construction area, near the stadiums. Displays along the path describe construction activities, machinery at work and the area’s history.
Visitors to Milepost 31 can browse through four sections:
You are here: Similar to the "you are here" points on maps, this section orients visitors to Milepost 31. It tells the story of the land upon which you are standing from the perspective for several different historical figures.
Moving Land: This section examines how the natural forces of glaciers, earthquakes and volcanoes have transformed Seattle's landscape during the past 20,000 years. Visitors will also learn about our own effects on the land, from the filling of the tidelands in Pioneer Square to the various regrade projects across the city.
Moving People: This section tracks transportation over time, with an emphasis on Pioneer Square. Visitors will see how people-moving has changed - and in some cases stayed the same.
Moving Forward: This section is all about tunneling. Visitors will learn about the history of tunneling technology, tunneling in Seattle and, of course, the SR 99 Tunnel Project. In addition, exhibits show visitors how the project - along with the Elliott Bay Seawall Replacement and Waterfront Seattle - will transform the future of Pioneer Square.
Why the name “Milepost 31”?
Mileposts mark progress. They help you track where you are on your journey, reminding you of the places you’ve passed through on your way to somewhere else.
But what if a milepost is so interesting that it becomes a destination? Located on SR 99 at the western edge of Pioneer Square, Milepost 31 is that kind of place. It marks a spot on the highway, but it also marks the spot where, before mileposts existed, mile-thick glaciers gave way to native civilizations. It’s where Seattle’s first neighborhood saw the rise of the city’s most notorious stretch of highway - the SR 99 Alaskan Way Viaduct - and where crews building the world’s largest diameter bored tunnel to replace the viaduct will first cross into the soils beneath Pioneer Square.
If you have questions about Milepost 31 please call the program hotline at 1-888-AWV-LINE, which is answered by staff between 8 a.m. and 5 p.m. on weekdays.